EP0725024B1

EP0725024B1 - Sheet feeding device having a movable bearing means cooperating in the guiding of the sheets along a transfer path and acted on by a pushing means

Info

Publication number: EP0725024B1
Application number: EP19960400214
Authority: EP
Inventors: Noburo Nakatani; Alexandre Dodge; Christophe Truffaut; Marie-Hélène Froger; Stéphane Michel
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1995-02-01
Filing date: 1996-01-31
Publication date: 2000-04-26
Anticipated expiration: 2016-01-31
Also published as: FR2729938A1; DE69607873T2; EP0725024A1; DE69607873D1

Description

The present invention relates to a sheet feeding device designed to transfer, one by one, sheets forming part of a pile to a device for processing the said sheets.
The present invention essentially finds an application in facsimile machines, notably as a device for feeding documents to be sent. It also finds an application as a sheet feeding device for a printing device, whether it be a printer, a photocopier or a facsimile machine. It can, in a general manner, find an application in the field of office automation, and other fields in which it is necessary to transfer one by one the sheets forming part of a pile along a predetermined path notably having two branches forming an angle, to a device for processing the said sheets.
The term processing is therefore to be regarded as encompassing:

the reading or analysis of items of information carried by the sheets,
the formation of images on the sheets, for example by printing, and
more generally, any use or transformation of the sheets by the processing device.

Figures 1a and 1b, which are diagrammatic views in partial longitudinal section of a device of the prior art enable the technical problem which faced the inventors to be understood.
The feeding device 10 which is depicted therein has, in the first place, a temporary storage area 11, here inclined with respect to the horizontal, and consisting, in this instance, of a plate the size of which is sufficient to be able to receive a pile of sheets 12, four of these having been depicted diagrammatically in cross section, with a deliberately exaggerated thickness in order for the technical problem to be more readily understood. The device 10 is designed to enable the sheets to be made to advance one by one from the pile 12 along a predetermined transfer path 13 (illustrated using a dotted line in Figure 1a). It can be observed that the path 13 has two branches 13a and 13b forming an angle (obtuse in the embodiment illustrated in the figure) and joined at this angle by means of a rounded portion 13c. The path 13 has an entry area and an exit area. The entry area is disposed immediately downstream of the temporary storage area 11.
In the said entry area, the device has a separating drive roller 14 which is arranged so as to be in contact with a sheet 12a, which will, for the sake of convenience, be called the "first sheet", and which is disposed at one of the ends of the pile 12 (in this instance it is the sheet located at the bottom end of the pile 12). The roller 14 is also arranged so as to drive this sheet into a first part of the said path, in this instance the first branch 13a. To this end, it has a means for driving in rotation in the direction illustrated by the arrow 15.
The device also includes a friction device 16, which in this instance consists of a rubber blade bearing on the roller 14 in the direction shown by the arrow 16a, and which is also disposed at the entry to the path 13. The friction device 16 is adapted to generate, at least on the first sheet 12a, a friction whose direction (arrow 17) is substantially opposite to the direction of driving of the first sheet 12a, the value of the friction force being determined, having regard to the rubbing exerted by the roller 14 on the sheet 12a, so as to enable the said first sheet to be driven while retaining the rest of the sheets in the pile 12. The drive roller and the friction device thus separate the first sheet 12a from the rest of the pile 12.
It will be noted that the friction device can consist of means other than a blade: it can, for example, consist of a roller turning in such a way that the tangential speeds of the two rollers, in their area of contact, are in opposite directions.
The feeding device also has a guide device 18 designed to guide the first sheet from the first branch 13a of the path to the second 13b and arranged on a level with the angle formed in this instance by the section 13c. The guide device has two curved surfaces, one forming a lower guide device 19 and the other forming an upper guide device 20. These surfaces substantially follow the shape of the path 13, and are spaced apart so as to permit the sheet 12a at least to enter therein. In a conventional manner, in order to reduce rubbing, the guide surfaces 19 and 20 are divided up and borne by longitudinal extension ribs, and distributed over the width of the transfer path 13.
The feeding device also includes a downstream drive device 21, consisting in this instance of two rollers 22, 23, the directions of whose rotation are illustrated respectively by the arrows 22a, 22b, and which is located downstream of the path 13 and designed to drive the first sheet 12a towards the exit from this path, along the second branch 13b of the latter.
The device illustrated in Figure 1a functions as follows (see also Figure 1b).
The separation device formed by the roller 14 and the friction device 16 enables, as explained above, the first sheet 12a to be separated from the rest of the pile.
It will be noted with respect to this that the friction generated by the drive roller 14 on the sheet 12a is greater than the friction (cf arrow 17) on the sheet 12a resulting from all the friction forces acting on the latter, amongst which there are:

the friction force generated by the device 16,
that existing between the sheet 12a and the plate 11a of the temporary storage area 11,
that existing between the sheets 12a and 12b.

The sheet 12a is then driven by the roller 14 into the first part 13a of the path 13. The guide surfaces 19 and 20 then guide the sheet towards the downstream pair of rollers 22, 23. When the first sheet 12a reaches the latter, it is gripped by them and driven towards a processing device arranged downstream of the rollers 22, 23 which can, in the case of a facsimile machine, be a device for reading the documents consisting of sheets in the pile 12.
In the device illustrated in Figures 1a and 1b, the downstream pair of rollers 22, 23 carries the sheet 12a at a speed substantially greater than the roller 14. In a conventional manner, provision is made for combining the latter with a disengagement mechanism, which comes into action as soon as the sheet is gripped by the downstream rollers 22, 23.
All these devices are perfectly conventional, and well known to those skilled in the art. They are, moreover, used by the company CANON in several of the facsimile machines that it manufactures and markets.
Owing to the angular character of the path 13, the inventors were confronted with the problem which will now be explained.
When the sheet 12a is gripped by the downstream rollers 22, 23, and when, owing to their drive speed being faster than that of the roller 14, the latter is disengaged, the sheet 12a is subjected to tensions which can be analysed in the following simplified manner:

it is, on the one hand, subjected to a tractive force shown diagrammatically by the arrow 25, at the downstream pair of drive rollers 22, 23,
and, on the other hand, as it is still squeezed between the friction device 16 and the drive roller 14, it is subjected to a force in the direction of the arrow 17.

The sheet 12a is thus subjected to a resulting tension and tends to adopt the position shown diagrammatically by continuous lines in Figure 1b. It should be noted, in this respect, that it does not follow the ideal path 13 but, on the contrary, comes to rub against the rounded portion of the guide surface 20.
This unfavourable positioning of the sheet 12a entails the following drawbacks:

first of all, the resulting tension in the sheet tends to reduce the force corresponding to the arrow 16a and, in certain cases, to raise the elastic friction device 16,
and, the sheet is subjected to a unfavourable rubbing on the guide surface 20.

The fact that the force corresponding to the arrow 16a diminishes has the effect of reducing the friction force 17, which under certain conditions (depending on the type of paper, the temperature and humidity) may give rise to the simultaneous feeding of two or more sheets, the separation device formed by the friction device 16 and the drive roller 14 consequently no longer fulfilling its function. It will be understood that, within the context of a facsimile machine, such "multiple feeding" is detrimental.
Moreover, the fact that the sheet undergoes an additional rubbing, owing to the aforementioned tension, on the guide surface 20, is liable in certain cases to damage the document, for example by producing tracks thereon. It will be understood that, within the context of a facsimile machine, such a drawback is also detrimental.
In order to resolve these technical problems, the inventors thought first of all of reducing the space existing between the guide surfaces 19 and 20. However, such a solution is not satisfactory, since it entails significantly higher manufacturing tolerances for the various parts of the device illustrated in Figures 1a and 1b with, as a consequence, an increased manufacturing cost. Moreover, such a solution does not resolve the problem related to the high level of rubbing exerted on the document by the upper guide surface but, on the contrary, increases it. Finally, if the space between the guide surfaces 19 and 20 is unthinkingly reduced, there is a risk that the facsimile machine will no longer accept paper of all kinds under different conditions of temperature and humidity. This is because, under certain conditions, the paper comes to swell or curl, which means that the space between the guide surfaces 19 and 20 cannot be reduced excessively.
The primary object of the present invention is to resolve this technical problem.
In the state of the art, partial solutions have already been proposed. Thus, for example, in the machine described in the document US-A-5 102 115, a rotating member is provided which has a dual function (see Figures 1 and 2):

on the one hand, exerting a thrust on the sheet separation device formed by a rubber blade, so that the pressure on the latter is constant, which has the effect of preventing the rubber blade from being raised. Consequently, the device of the prior art enables, in principle, such a multiple feeding to be avoided,
and, on the other hand, forming an upper guide surface, replacing the guide surface 20 in the device described in relation to Figure 1a above, and arranged so that the force normally applied to the upper guide at the angle is directed towards the axis of rotation of the movable rotating member. Consequently, the latter acts as a fixed guide surface such as the guide surface described above in relation to Figure 1a. The document US-A-5 102 115 moreover makes provision, as a variant, for this second function to be fulfilled, of a guide device independent of the thrust device for the rubber blade.

The inventors considered that the mechanism described in the document US-A-5 102 115 is not satisfactory, in that high rubbing forces against the upper guide surface exist, owing to the fact that the forces resulting from the tensions applied to the sheet are all directed towards a fixed point. The rubbing forces resulting therefrom have the drawback mentioned above.
The inventors therefore considered it necessary to provide a device which would have a more flexible structure, able to "absorb" the resulting tension described above in relation to Figure 1 b.
Furthermore, they wished, in their new feeding device, to preserve as far as possible the structure described above in relation to Figures 1a and 1b, notably owing to the fact that it is already being manufactured for use in existing facsimile machines.
The present invention attains these objectives since it concerns a sheet feeding device designed to transfer sheets to a processing device along a predetermined transfer path having an entry and an exit and two branches forming an angle, the device having an upstream drive device disposed at the entry to the said path to feed a sheet into a first part of said path, a lower guide device designed to guide the sheet from the first branch to the second and arranged on a level with the said angle, a downstream drive device arranged downstream of the said path and designed partially to drive the sheet towards the exit from the said path over a second part of the latter, device characterised in that it also includes:

a bearing means movable in the plane of the said angle and arranged on a level with the latter opposite the lower guide device, for cooperating with the guiding of the sheet at the level of said angle, and,
a pushing means arranged so as to exert on the movable bearing means at least one predetermined force such that the movable bearing means opposes, at least partially, the resulting tension in the sheet, at least once the latter is cooperating with the said downstream drive device.

By virtue of these arrangements, the present invention fulfils the objectives that the inventors set for it.
It will, moreover, be noted that, by replacing the upper part of the fixed guide with a bearing means able to move in the plane of the angle formed by the two branches of the path, the present invention affords a guide arrangement which is particularly adaptable in its use.
The device according to the present invention is, moreover, capable of absorbing variable tension forces. Indeed, firstly, the inventors observed that the resulting tension in the sheet described in relation to Figure 1b above was liable to vary according to the quality of paper used, climatic conditions (temperature, humidity) and the number of sheets in the pile 12. Secondly, the inventors observed that the said resulting tension is liable to vary in the course of the transfer of the sheet, the latter being, for example, subjected to jolts. Such jolts can be generated, for example, in a facsimile machine in which the reading of a document sometimes takes place discontinuously owing to transmission problems. The present invention advantageously enables variable tension forces to be compensated for.
This is the case in particular when, in accordance with a preferred embodiment, the movable bearing means is arranged on the first branch of a lever while the pushing means has a spring exerting a pressure on the second branch of the lever. Such an elastic device is in fact particularly suited to absorbing variable forces within a predetermined range.
Advantageously, in the preferred embodiment of the present invention, the movable bearing means includes a means designed to reduce advantageously the friction on the first sheet at the level of the said angle and it preferably includes a roller.
When designed to transfer, one by one, sheets forming part of a pile to the processing device, the sheet feeding device of the present invention furthermore comprises a temporary storage area for the pile of sheets arranged upstream of the upstream drive device, the latter comprising an upstream drive roller disposed at the entry to the said path and arranged so as to be in contact with a first sheet disposed at one of the ends of the pile and drive it into a first part of the said path, a friction device disposed at the entry to the said path, opposite the drive roller and generating, at least on the said first sheet, a friction in a direction substantially opposite to the direction in which the said first sheet is driven, the drive roller and the friction device effecting the separation of the first sheet from the rest of the pile.
The present invention also proposes an image forming apparatus having a sheet feeding device as defined above.
The characteristics and advantages of the present invention will emerge from the description that follows with reference to the accompanying drawings in which:

Figures 1a and 1b have already been described,
Figure 2 is a highly simplified diagrammatic view in longitudinal section of an embodiment of the invention,
Figures 3 to 5 are alternative embodiments of Figure 2,
Figure 6 is a highly simplified view in longitudinal section of a facsimile machine including a feeding device in accordance with the preferred embodiment of the present invention,
Figure 7 is an enlarged view of the inset VII in Figure 6, the device being illustrated in cross section along the line VII-VII in Figure 9,
Figure 8 is a simplified exploded perspective view of the mounting of a movable compensation lever of the device of Figure 7,
Figure 9 is a plan view of a part of the device in the direction shown by the arrow IX in Figure 7, and
Figure 10 is an elevation view in cross section along the line X-X in Figure 9.

A first embodiment of a feeding device in accordance with the present invention will now be described in relation to Figure 2.
In this figure, elements common to Figures 1a and 1b bear the same reference numerals.
In accordance with the present invention, the upper part of the fixed guide surface 20 is replaced by a bearing means 30 able to move in the plane of the angle formed by the branches 13a and 13b of the path 13, that is to say in the plane of the drawing.
In this embodiment, the bearing means 30 is movable in a vertical direction, as illustrated by the double arrow 31.
In accordance with the invention, the device also has a pushing means 40, formed in this embodiment by a spring, arranged so as to exert on the movable bearing means 30 at least one predetermined force (determined in this instance by the characteristics of the spring). In this embodiment, the spring 40 is mounted compressed between a fixed point 41 on the structure of the feeding device and the movable bearing means 30. The vertical movement of the latter is guided by a guide means which can be of any type and which is here represented diagrammatically by rails 32a, 32b.
In operation, the bearing means 30 exerts on the sheet 12a, by means of the pushing means 40 formed by the spring, a force tending to keep the sheet on the ideal path 13 and in particular on the curved section 13c of this path.
According to an advantageous characteristic of this embodiment, the bearing means 30 includes a means designed to reduce the friction on the first sheet 12a at the level of the angle formed by the two branches 13a, 13b of the path 13. This friction reducing means consists here of a surface made of Teflon arranged at the bottom end 32 of the bearing means 30. Of course, other materials able to reduce friction can be suitable.
In the alternative embodiment of Figure 3, the bearing means 30 is replaced by a rotatable roller 33. The shaft 33a of the roller 33 is also able to move in the plane of the angle formed by the branches 13a and 13b of the path 13 (double arrow 31). The shaft 33a of the roller 33 is carried by a stirrup 34 which is guided in translation by rails depicted diagrammatically at 35a and 35b.
By means of the use of a roller, the friction on the sheet 12a is appreciably reduced. For the remainder, the structure is identical to that described in relation to Figures 1a, 1b and 2.
In the alternative embodiment illustrated in Figure 4, the shaft 33a of the roller 33 is carried by a stirrup 50 whose end supporting the shaft 33a forms the end of a first lever arm 51 of a so-called "compensation" lever 53. This lever is mounted so as to rotate about a shaft 54, which is fixed to the structure of the feeding device and consequently forms a fixed point. The end of the second lever arm 55 of the lever 53 is connected to a spring 56 here forming with the lever the pushing means. The compression spring 56 is mounted on a fixed point 57 of the structure of the feeding device.
In this embodiment, the spring 56 exerts a thrust on the end of the second lever arm 55, this thrust being retransmitted through the first lever arm 51 to the stirrup 50 carrying the shaft 33a of the roller 33. By means of this arrangement, it is possible to offset, with respect to the shaft 33a of the roller 33, the anchorage point of the spring 56. Furthermore, it is possible, depending on the geometric characteristics of the lever arms 51 and 55, to provide a lower-strength spring of reduced size, if need be.
Figure 5 illustrates, diagrammatically, another embodiment of the invention and a particular implementation of the device that has just been described in relation to Figure 4. In this figure, means identical or similar to those in Figure 4 bear the same reference numerals.
The temporary storage area 11, the drive roller 14, the friction device 16, the lower guide 19 and the ideal path 13 will be recognized. Downstream of the path 13 there are arranged rollers 22, 23, similar in function to the rollers described previously.
In accordance with this alternative embodiment, the movable bearing means 33 (a roller, in this instance) is also carried by a stirrup 50' at the end of the first arm 51' of a movable compensation lever 53'. The second arm 55' of the lever 53' cooperates with a spring 56' bearing on a fixed point 57' of the structure of the device.
In this embodiment, the axis 54' of rotation of the lever 53' is common with the axis of rotation of the upper downstream roller 22.
Such an arrangement enables one shaft to be dispensed with and, above all, enables the arrangement described in relation to Figures 1a and 1b to be used, partially at least, while avoiding the need to modify the structure in order to arrange a rotation axis 54' for the lever 53'.
In this embodiment, the shaft 54' is also able to move in translation, in the plane of the angle formed by the branches 13a and 13b of the path 13. The directions of translation are shown diagrammatically in Figure 5 by means of the double arrow 60.
The shaft 54' is guided in translation by means of a "horseshoe" guide 61 oriented in the direction shown by the double arrow 60. In this embodiment, the guide 61 is integrated into a guide 62 arranged downstream of the roller 33. The extension of the guide 62 is substantially rectilinear and, downstream of the roller 33, it fulfils the same guiding function as the part of the rigid guide 20 arranged downstream of the part 13c of the path 13 described in relation to Figures 1a and 1b above.
In this embodiment also, it can be seen that the anchorage point 57' of the spring 56' is arranged on a part of the guide 62 disposed downstream of the downstream drive rollers 22, 23.
A spring 64 is arranged between a fixed point 65 and the axis 54', so as to push the roller 22 towards the roller 23 in order to squeeze the transferred sheet.
By virtue of this arrangement, it is also possible to absorb certain manufacturing tolerances, more particularly in the positioning of the axis of the roller 23, notably when the upper roller 22 is fixed to a casing able to be separated from the rest of the structure, so that, in this latter case, the roller 22 can be moved away from the roller 23.
This arrangement moreover enables variations in the thickness of the sheets or in the documents of the pile 12 to be compensated for.
For the remainder, the operation of the device in Figure 5 is similar to that in Figure 4, the spring 56' exerting, by means of the lever 53', a thrust on the roller 33, here forming the movable bearing means within the meaning of the present invention. This force tends, in accordance with the invention, to keep the sheet on the ideal path 13 and in particular on the curved section 13c of this path.
A preferred embodiment of the feeding device in accordance with the invention, adapted for a facsimile machine, will now be described in relation to Figures 6 to 10.
In this embodiment, the device is, in principle, similar to the embodiment that has just been described in relation to Figure 5.
According to the chosen embodiment depicted in Figure 6, the feeding device is incorporated into a facsimile machine 100 having, in a conventional manner:

a temporary storage area 101 for documents to be sent, including a plate 102 on which the documents are stacked,
a reading device area 103 essentially having a reading head 104, and a bearing roller 105,
a printing device for received documents 106 essentially having a printing head 107 and a guide and bearing roller 108,
a storage tray for paper 109 arranged upstream of a device 110 for transferring the paper to the printing device 106, and
a sheet feeding device 200 in accordance with the invention and designed to transfer one by one the sheets stacked on the support plate 102 to the reading device 103.

In the facsimile machine 100 illustrated in cross section in Figure 6, part of the reading device (the roller 105) and of the feeding device is arranged in a casing 115 pivoting about an axis shown diagrammatically under the reference numeral 111. On the top of the casing 115 the control panel 112 of the facsimile machine is arranged. In Figure 6, the casing 115 is illustrated in unbroken lines in its closed position, in which the facsimile machine is operational. It is illustrated in dotted lines in its open position in which the user can intervene in the event of a paper jam, in order to unblock the facsimile machine. The casing 115 has, firstly, a frame 116 bearing various elements of the reading and feeding device, and, secondly, a cover 117 bearing the control panel 112.
Apart from the feeding device 200 which is the object of the present application, and its partial mounting in the frame 116, all the other devices and arrangements described briefly in relation to Figure 6 are conventional and as well known to those skilled in the art. These devices and arrangements will consequently not be described in greater detail here. It should, however, be noted that the storage tray 109 known in the state of the art can be replaced by that which is the object of French patent applications Nos 94.12993, 94.12994 and 94.12995 filed on 28 October 1994, the descriptions of which are incorporated herein by reference.
Figure 7 is an enlargement of the inset VII in Figure 6. It illustrates in greater detail the feeding device and the arrangement of the casing 115. Figures 8 to 10 enable the device to be better understood.
The feeding device includes, in addition to the storage plate 102, a separating drive roller 201, which is arranged so as to be in contact with the sheet at the bottom of a pile of sheets (in this instance of documents to be sent) disposed on the plate 102. The pile of sheets has been depicted under the reference numeral 12. The roller 201 is rotated in the direction shown by the arrow 202 by a geared motor drive device, not shown in this figure and having a conventional structure.
The device 200 also has a friction device 203 borne by the frame 116 and arranged in an opening 118 in the latter. In the chosen embodiment depicted, the friction device 203 has a rubber blade 204 mounted on a movable support 205, itself mounted so as to rotate by means of a shaft 206 (formed in this instance by journals fixed to the body of the framework 205) on bearings 119 on the frame 116 (see Figures 9, 10 notably).
The movable support 205 is pushed towards the roller 201, in the direction shown by an arrow 208, by means of a spring 209. In this embodiment, the spring 209 is a coil spring tensioned above the movable support 205 in order to exert the said pushing and attached to the frame 116 by hooks 114 (see Figure 8, in which the spring 209 is not depicted, and Figures 9, 10).
The feeding device also has a prestressing mechanism 210 designed to compress the pile of sheets 12 so as to ensure contact between the bottom sheet and the roller 201. The prestressing mechanism 210 includes, to this end, a lever 211 arranged, in this instance, so as to pivot about the shaft 206. The lever 211 includes a pair of lateral prestressing arms 212 and an actuation arm 213. A spring 214 is compressed between the actuation arm 213 and the movable support 205, to push the prestressing arms 212 towards the roller 201 through the pile of sheets 12.
The friction device 203, and in particular the movable support 205 and the spring 209, together with the prestressing mechanism 210, are the object of French patent application No 95.01163, whose content is incorporated herein by reference. Reference should therefore be made to that patent application for a more complete description of these devices.
The feeding device 200 also includes a downstream drive device formed in this instance by two downstream drive rollers, one lower 222, the other upper 223. The directions of rotation of these rollers are respectively depicted diagrammatically by the arrows 222a, 223a. The downstream drive rollers are designed to drive the sheet towards the exit from the path on which it is guided by the device described here. In this embodiment, only the lower downstream roller 222 is rotated by a geared motor device. The latter, of conventional structure, has not been depicted in the drawings.
The device 200 also has a guide device 220 having a divided guide surface 220a having substantially the same structure as the lower guide device 19 described above in relation to Figures 1a and 1b. The device 200 also has a guide device having a divided upper guide surface 280.
The surfaces 220a and 220b serve essentially to guide the sheet at its ends. The guiding of the sheet on its central part, which would be liable here to be subjected to the tensions mentioned above in relation to Figures 1a and 1b, is essentially effected by the means described below and illustrated in the figures.
As described in relation to Figure 1a, the peripheral speed of the rollers 222, 223 is substantially greater than that of the roller 201. Thus the geared motor system for driving the roller 201 includes, as in the state of the art, a disengagement system designed to come into action as soon as the sheet is squeezed by the downstream rollers 222, 223.
In accordance with the invention, the device 200 includes a movable bearing means in the plane of the angle formed by the transfer path (which extends here from the area of contact 270 between the roller 201 and the blade 204 to the area of contact 272 between the rollers 222 and 223).
In the embodiment chosen and depicted, the movable bearing means includes a bearing roller 233.
In the preferred embodiment described here, the roller 233 is mounted, as in the embodiment described in relation to Figure 5, on a movable compensation lever 240 whose point of rotation is common with the axis of the upper downstream roller 223.
The lever 240 is illustrated in exploded perspective in Figure 8. This lever is a moulded plastic component, arranged so as to house, firstly, the upper downstream drive roller 223 and the bearing roller 233. To this end, the lever 240 has a body 241 arranged so as to house the said rollers, and lateral cheeks 242, only one of the latter being visible in Figure 8. The cheeks 242 each have two bearings, one 243 designed to carry the shaft 225 of the roller 223 and the other 244 being arranged so as to carry a journal 226 arranged at each of the ends of the roller 233 and coaxial with the latter. The bearings 243 and 244 are arranged so as to allow the free relative rotation of the shaft 225 and journals 226 with the bearings 243, 244. The roller 223 is also free to turn relative to the shaft 225.
The lever 240 has, arranged on each side of the axis VII-VII, a stop 248 having a centring lug 249 (Figure 7) for a spring 250 arranged so as to be compressed between the stop 248 and a bearing surface 251 fixed to the frame 116.
The shaft 225, which passes through the body of the lever 240 and that of the roller 223, extends, as seen in Figures 8 and 9, beyond the lateral cheeks 242 of the lever 240.
The frame 116 carries two bearings 227 moulded with this frame, themselves having a notch 228. Each notch 228 is adapted to receive one end of the shaft 225, while allowing the latter limited translation in the direction shown by the double arrow 229 (Figure 8).
The device also has two springs 252 equivalent to the spring 64 described above in relation to Figure 5. In this embodiment, these springs, which are leaf springs here, are arranged so as to exert a downward pressure on the shaft 225, only one of these having been depicted in Figure 8. Each leaf spring 252 has a mounting section 253 and an active section 254. The mounting section 253 enables the spring to be mounted on the frame 116 by means of a screw 258. The active section has a section 259 at the end of which there are folded two flanges 255 each having an edge 256 coming to bear on the shaft 225 (see Figures 8 and 10).
In accordance with the normal practice for facsimile machines, a double system for detecting the front end of sheets, designed to facilitate loading, is also provided. This device, whose structure is conventional, will not be described in detail here. It should, however, be noted that it informs the user that the documents are correctly loaded in the temporary storage area 101, and initiates, after a certain delay, the rotation of the roller 201 and the driving of the sheet in order for it to be read by the device 103.
It should also be noted that the movable support 205 has two retaining arms 306, designed to limit, in cooperation with the frame 116, the angular travel of the movable support 205 when the casing 115 is in the open position (dotted lines) in Figure 6 (see also Figure 9).
The device operates as follows.
The lever 240 is held in place by the shaft 225, which is engaged in the notches 228 in the bearings 227. The springs 252 bear, through the edges 256, on the shaft 225, so that the roller 223 is pushed towards the roller 222. When the device is empty, the roller 223 bears on the lower drive roller 222. This device, by virtue of the action of the leaf springs 252:

notably compensates for different paper thicknesses, giving the roller 223 a mobility in its axis of rotation in translation in the direction shown by the double arrow 229 (Figure 8);
compensates for any relative differences in positioning of the rollers 222 and 223 resulting from manufacturing tolerances. As a matter of fact, as the upper downstream drive roller 223 is mounted on a movable casing, the relative positioning of the axes of the downstream drive rollers can be critical. This drawback is overcome by the aforementioned mounting of the shaft 225;
affords a squeezing force of a predetermined value between the rollers 222 and 223.

The movable bearing roller 233 is pushed towards the guide surface 220a by the spring 250. It will be observed that the roller 233 is in fact arranged at the end of a first lever arm formed by the separation between the axes of rotation of the roller 223 and of the roller 233. The distance between the axis of the shaft 225, which forms in this instance the bearing point of the lever, and the bearing surface 260 of the stop 248, for the spring 250, forms the second lever arm.
In the embodiment described here, retaining means (not given a reference numeral) are arranged in the casing and on the stop 248, to limit the rotation of the lever 240 about the shaft 225, when the casing is in its open position (shown in dotted lines in Figure 6).
By virtue of these arrangements, the sheets transferred from the temporary storage area 102 to the reading area 105 are guided perfectly along thetransferpathpassingthroughthefollowingareas(see Figure 10):

the area of contact 270 between the drive and separation roller 201 and the elastic blade 204,
the area 271 of the roller 233 facing the guide surface 220a, marking the angle of the transfer path and similar to the curved section 13c illustrated notably in Figures 2 to 5,
the area of contact 272 between the downstream drive rollers 222 and 223.

The movable bearing means formed here by the roller 233 absorbs the variable tensions present in the central part of the sheet and described above in relation to Figures 1a and 1b.
It should, moreover, be observed that, by arranging the movable bearing roller 233 on a lever having as its axis of rotation that of the upper downstream drive roller 223, the need to arrange elsewhere in the structure of the movable casing an axis of rotation for the lever carrying the roller 233 is avoided, since the shaft of the upper downstream drive roller 223 is advantageously used. In addition, the arrangement of this shaft in bearings such as the bearings 227 having the notch 228, in cooperation with the elastic bearing means 252, affords the advantages outlined above.
Furthermore, it should be noted that the mounting of the roller 233 on a movable compensation means such as the lever 240 enables any variations due to manufacturing tolerances in the positioning of the axis of the roller 223 to be compensated for. This is particularly advantageous when the roller 223 is mounted, as here, on a movable casing.
All these arrangements thus enable a feeding device to be produced, notably for a facsimile machine, which does not have the drawbacks mentioned in relation to the state of the art, while at the same time remaining adaptable in its use, since some of these elements can be mounted on a movable casing.
Of course, the present invention is not in any way limited to the embodiment chosen and depicted, but, quite the contrary, encompasses any alternative embodiment within the reach of those skilled in the art.
In particular, the friction device formed by a blade can be replaced by any other means, and notably a roller such as that described above.

Claims

Sheet feeding device (10) designed to transfer sheets to a processing device along a predetermined transfer path (13; 270, 271, 272) having an entry (270) and an exit (272) and two branches (13a, 13b) forming an angle (13c; 271), the device (10) having an upstream drive device (14, 16) disposed at the entry to said path to feed a sheet into a first part of said path, a lower guide device (19; 220) designed to guide the sheet from the first branch to the second and arranged on a level with the said angle, a downstream drive device (21; 222, 223) arranged downstream of the said path and designed partially to drive the sheet towards the exit from the said path over a second part of the latter, feeding device characterized in that it also includes:

a bearing means (33; 233) movable in the plane of the said angle and arranged on a level with the latter opposite the lower guide device, for cooperating with the guiding of the sheet at the level of said angle, and

a pushing means (56; 56'; 250) arranged so as to exert on the movable bearing means at least one predetermined force such that the movable bearing means (33; 233) opposes, at least partially, the resulting tension in the sheet, at least once the latter is cooperating with the said downstream drive device.
Sheet feeding device according to Claim 1, designed to transfer, one by one, sheets forming part of a pile to the processing device, characterized in that it furthermore comprises a temporary storage area (11; 101) for the pile of sheets (12) arranged upstream of the upstream drive device (14, 16), the latter comprising an upstream drive roller (14; 201) disposed at the entry to the said path and arranged so as to be in contact with a first sheet (12a) disposed at one of the ends of the pile and drive it into a first part of the said path, a friction device (16; 203) disposed at the entry to the said path, opposite the drive roller and generating, at least on the said first sheet, a friction (17) in a direction substantially opposite to the direction in which the said first sheet is driven, the drive roller (14; 201) and the friction device effecting the separation of the first sheet from the rest of the pile.
Feeding device according to Claim 1 or 2, characterized in that the said movable bearing means includes a means designed to reduce the friction on the said first sheet at the levl of the said angle.
Feeding device according to Claim 3, characterized in that the said friction reducing means includes a roller (33; 233).
Feeding device according to Claim 1 or 4, characterised in that the said movable bearing means is arranged on a lever (53, 53', 240) whilst the pushing means (56; 56'; 250) is adapted to exert a thrust on the lever.
Feeding device according to Claim 4 or 5, characterised in that the said movable bearing means (33; 233) is mounted on a movable compensation means (53'; 240).
Feeding device according to Claim 6, characterised in that the movable compensation means includes a lever (53'; 240) whose axis of rotation (54'; 225) is common with the axis of rotation of an upper downstream roller (22; 223) of the downstream drive device (21; 222, 223).
Feeding device according to Claim 7, characterised in that the said lever (53'; 240) and the said downstream roller (22; 223) are mounted on the said feeding device in such a way that the said axis of rotation (54'; 225) is movable in translation.
Image forming apparatus having a sheet feeding device according to any one of Claims 1 to 8.